CN104965112A - Electric power system current quality assessment method - Google Patents

Abstract

The invention belongs to the electric energy quality analysis field, especially an electric power system current quality assessment method. The method comprises: firstly, performing Fourier decomposition on the voltage and current detected at a PCC, and dividing a voltage subset and a current subset obtained after decomposition into a harmonic portion and an interharmonic portion; secondly, for the harmonic portion, based on the harmonic wave power direction of each frequency, calculating harmonic voltages and harmonic current to obtain a current component under each frequency, and decomposing active current, diffusion current, reactive current, unbalanced current, zero sequence current and generation current; and finally, calculating each current component to obtain required current quality assessment indicators, i.e., a rate of equipment utilization, system operation efficiency, reactive current, zero sequence current, unbalanced current, reactive current fluctuation quantity and frequentness, generation current, diffusion current and interharmonic current. The assessment indicators are corresponding with real current quality phenomena one by one; an assessment system has clear concepts, and can effectively assess current quality in real engineering.

Description

A kind of method for the assessment of electric system current quality

Technical field

The invention belongs to power quality analysis field, particularly relate to a kind of method for the assessment of electric system current quality.

Background technology

Along with the progress in epoch, power electronic equipment transformation of electrical energy and and network process in effect more and more important, range of application is also more and more wider, but meanwhile, the use of these nonlinear devices brings the power quality problems such as even more serious harmonic distortion to electrical network; In addition, the fast development of high ferro technology etc., the single phase property of electrical traction load also can aggravate the three-phase imbalance of electrical network.The monitoring of electric power quality, assessment and improvement nowadays ensure that electrical network normally runs the link that can not be ignored.

The electricity quality evaluation system of current China is tentatively built up, and existing electricity quality evaluation system is mainly based upon on the basis of quality of voltage assessment.Quality of voltage generally includes voltage deviation, electric voltage frequency deviation, Voltage unbalance, voltage fluctuation and flicker, voltage dip (rising temporarily) and interruption, voltage harmonic, voltage transients, voltage trap, under-voltage, superpotential etc.In current quality of voltage evaluation process, mainly study the first six.But not yet there is the assessment carried out for current parameter.

The theory of current's physical components (CPC is theoretical) that Czarnecki proposes, is considered to one of the most promising Power Theory at present.CPC is theoretical on the basis in conjunction with actual physics phenomenon, use the concept such as lump, equivalence, redefine the quantity of power under the uneven condition of non-sinusoidal, be active power, dispersion power, reactive power, imbalance power and generation power five kinds of components by traditional power divider, electric current is also broken down into active current, scattered current, reactive current, out-of-balance current and generation electric current simultaneously.Wherein, concept and the traditional concept of active power and reactive power are similar, characterize the meritorious of load and reactive power consumption; Dispersion power characterizes the distortion of system to a certain extent; Imbalance power is the power that the negative-sequence current flowed under each frequency of load by power supply produces, and the uneven characteristic sum characterizing load causes the unbalancedness of voltage; There is the nonlinear effect that power embodies load.

The present invention is just based on above background, on the basis of CPC theory, corresponding with quality of voltage, start with from the evaluation index of quality of voltage, according to feature and the actual needs of electric current, invent a kind of current quality appraisal procedure being similar to quality of voltage assessment, using the current component based on CPC theory as basic parameter, reflect the situations such as the power factor of electric system, imbalance and harmonic distortion.

Summary of the invention

In order to comprehensively assess current quality, and provide data and theoretical foundation for electric energy metrical, electricity quality evaluation and improvement etc., the present invention proposes a kind of method for the assessment of electric system current quality, comprising:

Step 1: in each spectrum analysis time window, gathers the voltage and current signal at electric system points of common connection place;

Step 2: the voltage and current signal collected is carried out Fourier decomposition, obtains voltage and current harmonic wave collection N and m-Acetyl chlorophosphonazo collection N _i;

Step 3: according to the voltage and current harmonic wave collection N described in step 2 and m-Acetyl chlorophosphonazo collection N _i, calculate the active power of nth harmonic and m-Acetyl chlorophosphonazo, n ∈ M, M are the number of times of harmonic waves all in system and m-Acetyl chlorophosphonazo subset;

Step 4: according to the direction of the nth harmonic active power described in step 3, is divided into two subset N by harmonic wave _cwith subset N _d, m-Acetyl chlorophosphonazo is divided into two subset N _iCwith subset N _iD;

Described subset N _c, N _iCrepresent that the direction of active power is harmonic wave from power supply to load and m-Acetyl chlorophosphonazo subset respectively, described subset N _d, N _iDrepresent that the direction of active power is harmonic wave from load to power supply and m-Acetyl chlorophosphonazo subset respectively;

Step 5: according to the subset N described in step 4 _cwith subset N _d, harmonic current subset is wherein divided into forward harmonic current subset N _cIwith negative sense harmonic current subset N _dI, according to the subset N described in step 4 _iCwith subset N _iD, m-Acetyl chlorophosphonazo electric current subset is wherein divided into forward m-Acetyl chlorophosphonazo electric current subset N _iCIwith negative sense m-Acetyl chlorophosphonazo electric current subset N _iDI;

Step 6: according to the negative sense harmonic current subset N described in step 5 _dIwith negative sense m-Acetyl chlorophosphonazo electric current subset N _iDI, for there is current i in corresponding electric current _g, and use i _gthe current harmonics cause load and m-Acetyl chlorophosphonazo are assessed;

Step 7: according to the forward harmonic current subset N described in step 5 _cIwith forward m-Acetyl chlorophosphonazo electric current subset N _iCIit is decomposed further;

Situation 1, if electric system is monophase system, then decomposites active current, scattered current and reactive current; Calculate system total voltage root-mean-square valve V and electric current r.m.s. I; By active current and equipment rated current I _nradiometer calculate plant factor, calculate running efficiency of system by the radiometer of active current and electric current r.m.s. I; Variation in voltage limit value required by system, voltage root-mean-square valve V and system impedance calculate reactive current variation and frequency;

Situation 2, if electric system is three-phase three-line system, then decomposites active current, scattered current, reactive current and out-of-balance current; Calculate system total voltage root-mean-square valve V and electric current r.m.s. I; By active current and equipment rated current I _nradiometer calculate plant factor, calculate running efficiency of system by the radiometer of active current and electric current r.m.s. I; Variation in voltage limit value required by system, voltage root-mean-square valve V and system impedance calculate reactive current variation and frequency;

Situation 3, if electric system is three-phase four-wire system, then decomposites active current, scattered current, reactive current, out-of-balance current and zero-sequence current; Calculate system total voltage root-mean-square valve V and electric current r.m.s. I; By active current and equipment rated current I _nradiometer calculate plant factor, calculate running efficiency of system by the radiometer of active current and electric current r.m.s. I; Variation in voltage limit value required by system, voltage root-mean-square valve V and system impedance calculate reactive current variation and frequency;

Step 8: the voltage and current signal gathering electric system points of common connection place in future time window, recalculates by described step 2-7 and upgrades each current quality evaluation index;

Step 9: by described step 8 double counting 14 times, when equaling 200ms each computing time, carrying out seamless accumulation to 15 values of each index obtained, obtaining 3s accumulated value;

Step 10: repeatedly calculate by step 1-9 and upgrade each current quality evaluation index 3s accumulated value.

Described each current quality evaluation index comprises economic evaluation index and restricted evaluation index; Belong to having of economic evaluation index: plant factor η ₁, running efficiency of system η ₂, reactive current i _r, zero-sequence current i _0n; Belong to having of restricted evaluation index: comprise out-of-balance current i _u, reactive current undulate quantity and frequency △ I _r, there is current i _g, scattered current i _s, m-Acetyl chlorophosphonazo electric current.

Described plant factor η ₁characterization device is utilized the ratio with transmitting active power; Described running efficiency of system η ₂characterization system is in operation the ratio of effective transmitting active power; Described reactive current i _rthe reactive power that reflected load consumes and the idle via net loss caused of transmission; Described zero-sequence current i _0nembody the unbalancedness of load and the power attenuation of the neutral line; Described out-of-balance current i _uembody the unbalancedness of load and cause the unbalancedness of voltage; Described reactive current undulate quantity and frequency △ I _rthe order of severity of reflection reactive load power variation and the fluctuation of voltage and frequency; Described generation current i _gcharacterize the current distortion that load causes; Described scattered current i _sthe current distortion that characterization system causes; Described m-Acetyl chlorophosphonazo electric current characterizes the m-Acetyl chlorophosphonazo content of system power.

Beneficial effect of the present invention is: the current quality appraisal procedure that the present invention proposes, be applicable to monophase system, the three-phase three-wire system of power supply symmetry or three-phase four-wire system, highly versatile, and the clear physical concept corresponding to index, clear thinking, the scope of applicable system is wider.

Accompanying drawing explanation

Fig. 1 is the corresponding relation figure of each current quality evaluation index.

Embodiment

Below in conjunction with accompanying drawing, embodiment is elaborated.

Embodiment 1: monophase system

Step 1: in each spectrum analysis time window T, the voltage v current signal i of acquisition system PCC point;

Step 2: the voltage and current signal collected is carried out Fourier decomposition, obtains the waveform collection of voltage, electric current, is the measurement window of 10 cycles, thus can obtains harmonic wave collection N and m-Acetyl chlorophosphonazo collection N simultaneously due to what take in the calculation _i, required is the harmonic wave of electric current and the harmonic wave subset of m-Acetyl chlorophosphonazo subset and voltage here;

$i=\underset{n\∈M}{\Σ}{i}_n---\left(1\right)$

$I_{ig.n}=\sqrt{\underset{i=2}{\overset{8}{\Σ}}{I}_{k+i}^2}---\left(2\right)$

$v=\underset{n\∈M}{\Σ}{v}_n---\left(3\right)$

Step 3: according to the voltage and current harmonic wave collection N described in step 2, calculate the active power of nth harmonic and m-Acetyl chlorophosphonazo, n ∈ M, M are the number of times of harmonic waves all in system and m-Acetyl chlorophosphonazo subset;

$P_n=\mathrm{Re}\left\{V_n{I}_n^{*}\right\}---\left(4\right)$

Step 4: according to the nth harmonic described in step 3 and the active power direction under m-Acetyl chlorophosphonazo, harmonic wave is divided into subset N _cwith subset N _d, m-Acetyl chlorophosphonazo is divided into subset N _iCwith subset N _iD;

P _n>0, n ∈ N _cor N _iC; P _n<0, n ∈ N _dor N _iD(5)

Described subset N _c, N _iCrepresent that active power direction is harmonic wave from power supply to load and m-Acetyl chlorophosphonazo subset respectively, described subset N _d, N _iDrepresent that active power direction is harmonic wave from load to power supply and m-Acetyl chlorophosphonazo subset respectively;

Step 5: according to the subset N described in step 4 _cwith subset N _d, harmonic current subset is wherein divided into subset N _cIwith subset N _dI, according to the subset N described in step 4 _iCwith subset N _iD, m-Acetyl chlorophosphonazo electric current subset is wherein divided into forward m-Acetyl chlorophosphonazo electric current subset N _iCIwith negative sense m-Acetyl chlorophosphonazo electric current subset N _iDI;

Step 6: according to the negative sense harmonic current subset N described in step 5 _dIwith negative sense m-Acetyl chlorophosphonazo electric current subset N _iDI, for there is current i in corresponding electric current _g, and use i _gthe current harmonics cause load and m-Acetyl chlorophosphonazo are assessed;

Step 7: according to the forward harmonic current subset N described in step 5 _cIwith forward m-Acetyl chlorophosphonazo electric current subset N _iCIit is decomposed further;

Active current is

$i_a=G_{e}v=G_e{V}_0+\sqrt{2}\mathrm{Re}\underset{n\&Element;N_{CI},N_{iCI}}{\&Sigma;}{G}_e{V}_n{e}^{{\mathrm{jn\&omega;}}_{1}t}---\left(6\right)$

Scattered current is

$i_s=(G_0-G_e)V_0+\sqrt{2}\mathrm{Re}\underset{n\&Element;N_{CI},N_{iCI}}{\&Sigma;}(G_n-G_e)V_n{e}^{{\mathrm{jn\&omega;}}_{1}t}---\left(7\right)$

Reactive current is

$i_r=\sqrt{2}\mathrm{Re}\underset{n\&Element;N_{CI},N_{iCI}}{\&Sigma;}{\mathrm{jB}}_n{V}_n{e}^{{\mathrm{jn\&omega;}}_{1}t}---\left(8\right)$

Described parameter can be obtained by following formulae discovery:

Load equivalent conductance is G _e=P/||v|| ², V _nfor the voltage phasor of each frequency.

Total voltage and electric current root-mean-square valve are

$V=\sqrt{\underset{n\&Element;M}{\&Sigma;}{v}_n^2}---\left(9\right)$

$I=\sqrt{\underset{n\&Element;M}{\&Sigma;}{i}_n^2}---\left(10\right)$

Plant factor is

${\mathrm{\&eta;}}_1=\frac{I_a}{I_N}---\left(11\right)$

Running efficiency of system is

${\mathrm{\&eta;}}_2=\frac{I_a}{I}---\left(12\right)$

Reactive current variation and frequency are

${\mathrm{\&Delta;I}}_r=\frac{dV}{Z_s}---\left(13\right)$

Step 8: the voltage and current signal gathering system PCC point place in future time window, recalculates by described step 2-7 and upgrades each current quality evaluation index;

15 values of each index obtained are combined, obtain 3s combined value by step 9: by described step 8 double counting 14 times;

Described ageing adopts the account form of root-mean-square valve.For certain current component, suppose needing to carry out in the time period of ageing, the root-mean-square valve of the n calculated 10 cycles is I _10n, then the root-mean-square valve I after ageing is

$I=\sqrt{\frac{1}{n}\underset{n}{\&Sigma;}{I}_{10n}^2}---\left(14\right)$

Step 10: repeatedly calculate by step 1-9, can obtain the 3s calculated value of each current quality evaluation index.

Embodiment 2: three-phase three-line system

Step 1: in each spectrum analysis time window T, the voltage v of acquisition system PCC point _a, v _b, v _cwith current signal i _a, i _b, i _c;

Step 2: according to the voltage and current signal in this time window described in step 1, voltage and current signal is carried out Fourier decomposition, obtain the waveform collection of voltage, electric current, be the measurement window of 10 cycles due to what take in the calculation, thus can obtain harmonic wave collection N and m-Acetyl chlorophosphonazo collection N simultaneously _i, required is the harmonic wave of electric current and the harmonic wave subset of m-Acetyl chlorophosphonazo subset and voltage here;

$i_{\&perp;}=\underset{n\&Element;M}{\&Sigma;}{i}_{\&perp;n}\left(\&perp;=A,B,C\right)---\left(15\right)$

$I_{\&perp;ig.n}=\sqrt{\underset{i-2}{\overset{8}{\&Sigma;}}{I}_{\&perp;(k+i)}^2}\left(\&perp;=A,B,C\right)---\left(16\right)$

$v_{\&perp;}=\underset{n\&Element;M}{\&Sigma;}{v}_{\&perp;n}\left(\&perp;=A,B,C\right)---\left(17\right)$

Step 3: according to the voltage and current harmonic wave collection N described in step 2 and m-Acetyl chlorophosphonazo collection N _i, calculate nth harmonic and m-Acetyl chlorophosphonazo active power, n ∈ M, M are the number of times of harmonic waves all in system and m-Acetyl chlorophosphonazo subset;

$P_n=\mathrm{Re}\left\{\left(V_{An}{I}_{An}^{*}+V_{Bn}{I}_{Bn}^{*}+V_{Cn}{I}_{Cn}^{*}\right)\right\}---\left(18\right)$

Step 4: according to the nth harmonic described in step 3 and the active power direction under m-Acetyl chlorophosphonazo, harmonic wave is divided into subset N _cwith subset N _d, m-Acetyl chlorophosphonazo is divided into subset N _iCwith subset N _iD;

P _n>0, n ∈ N _cor N _iC; P _n<0, n ∈ N _dor N _iD(19)

Described subset N _c, N _iCrepresent that active power direction is harmonic wave from power supply to load and m-Acetyl chlorophosphonazo subset respectively, described subset N _d, N _iDrepresent that active power direction is harmonic wave from load to power supply and m-Acetyl chlorophosphonazo subset respectively;

Step 5: according to the subset N described in step 4 _cwith subset N _d, harmonic current subset is wherein divided into subset N _cIwith subset N _dI, according to the subset N described in step 4 _iCwith subset N _iD, m-Acetyl chlorophosphonazo electric current subset is wherein divided into forward m-Acetyl chlorophosphonazo electric current subset N _iCIwith negative sense m-Acetyl chlorophosphonazo electric current subset N _iDI;

Step 6: according to the negative sense harmonic current subset N described in step 5 _dIwith negative sense m-Acetyl chlorophosphonazo electric current subset N _iDI, for there is current i in corresponding electric current _g, and use i _gthe current harmonics cause load and m-Acetyl chlorophosphonazo are assessed;

Step 7: according to the forward harmonic current subset N described in step 5 _cIwith forward m-Acetyl chlorophosphonazo electric current subset N _iCIit is decomposed further;

Active current is

$i_a=G_{e}v=G_e{V}_0+\sqrt{2}\mathrm{Re}\underset{n\&Element;N_{CI},N_{iCI}}{\&Sigma;}{G}_e{V}_n{e}^{{\mathrm{jn\&omega;}}_{1}t}---\left(20\right)$

Scattered current is

$i_s=(G_0-G_e)V_0+\sqrt{2}\mathrm{Re}\underset{n\&Element;N_{CI},N_{iCI}}{\&Sigma;}(G_n-G_e)V_n{e}^{{\mathrm{jn\&omega;}}_{1}t}---\left(21\right)$

Reactive current is

$i_{rn}=\sqrt{2}\mathrm{Re}\underset{n\&Element;N_{CI},N_{iCI}}{\&Sigma;}{\mathrm{jB}}_n{V}_n{e}^{{\mathrm{jn\&omega;}}_{1}t}---\left(22\right)$

Out-of-balance current is

$i_{un}=i_n-i_{an}-i_{rn}=\sqrt{2}\mathrm{Re}\underset{n\&Element;N_{CI},N_{iCI}}{\&Sigma;}{A}_n{V}_n^{\#}{e}^{{\mathrm{jn\&omega;}}_{1}t}---\left(23\right)$

Described parameter can be obtained by following formulae discovery:

Three-phase equivalent admittance is

G _e＝P/||v _n|| ²(24)

In CPC theory, Y _n=G _n+ jB _n=Y _aBn+ Y _bCn+ Y _cAnbe leg-of-mutton type of attachment by the load equivalent of three-phase three-wire circuit, thus its resultant admittance is, calculates conductance and susceptance respectively:

$G_n=P_n/{\left|\right|v_n\left|\right|}^2=\mathrm{Re}\left\{\left(V_{An}{I}_{An}^{*}+V_{Bn}{I}_{Bn}^{*}+V_{Cn}{I}_{Cn}^{*}\right)\right\}/{\left|\right|v_n\left|\right|}^2,n\&Element;N_{CI},N_{iCI}---\left(25\right)$

$B_n=-Qh/{\left|\right|v_n\left|\right|}^2=-Im\left\{\left(V_{An}{I}_{An}^{*}+V_{Bn}{I}_{Bn}^{*}+V_{Cn}{I}_{Cn}^{*}\right)\right\}/{\left|\right|v_n\left|\right|}^2,n\&Element;N_{CI},N_{iCI}---\left(26\right)$

Wherein, $\left|\right|v_n\left|\right|=\sqrt{{\left|\right|v_{\mathrm{An}}\left|\right|}^2+{\left|\right|v_{\mathrm{Bn}}\left|\right|}^2+{\left|\right|v_{\mathrm{Cn}}\left|\right|}^2}.$

Uneven admittance is

$A_n=-(Y_{BCn}+{\mathrm{\&alpha;}}_n{Y}_{CAn}+{\mathrm{\&alpha;}}_n^{*}{Y}_{ABn})=A_n{e}^{{\mathrm{j\&psi;}}_n},n\&Element;N_{CI},N_{iCI}---\left(27\right)$

Wherein, α _n=e ^{jn120 °}, for α _nconjugation.

Voltage vector is respectively: $V_0=\left(\begin{array}{c}{V}_{A0}\\ V_{B0}\\ V_{C0}\end{array}\right),V_n=\left(\begin{array}{c}{V}_{An}\\ V_{Bn}\\ V_{Cn}\end{array}\right),V_n^{\#}=\left(\begin{array}{c}{V}_{An}\\ V_{Cn}\\ V_{Bn}\end{array}\right).$

Total voltage and electric current root-mean-square valve are

$V=\sqrt{\underset{n\&Element;M}{\&Sigma;}(V_{An}^2+V_{Bn}^2+V_{Cn}^2)}---\left(28\right)$

$I=\sqrt{\underset{n\&Element;M}{\&Sigma;}(I_{An}^2+I_{Bn}^2+I_{Cn}^2)}---\left(29\right)$

Plant factor is

${\mathrm{\&eta;}}_1=\frac{I_a}{I_N}---\left(30\right)$

Running efficiency of system is

${\mathrm{\&eta;}}_2=\frac{I_a}{I}---\left(31\right)$

Reactive current variation and frequency are

${\mathrm{\&Delta;I}}_r=\frac{dV}{Z_s}---\left(32\right)$

Step 8: the voltage and current signal gathering system PCC point place in future time window, recalculates by described step 2-7 and upgrades each current quality evaluation index;

15 values of each index obtained are combined, obtain 3s combined value by step 9: by described step 8 double counting 14 times;

Described ageing adopts the account form of root-mean-square valve.For certain current component, suppose needing to carry out in the time period of ageing, the root-mean-square valve of the n calculated 10 cycles is I _10n, then the root-mean-square valve I after ageing is

$I=\sqrt{\frac{1}{n}\underset{n}{\&Sigma;}{I}_{10n}^2}---\left(33\right)$

Step 10: repeatedly calculate by step 1-9, can obtain the 3s calculated value of each current quality evaluation index.

Embodiment 3: three-phase four-wire system

Step 1: in each spectrum analysis time window T, the voltage v of acquisition system PCC point _a, v _b, v _cwith current signal i _a, i _b, i _c;

Step 2: according to the voltage and current signal in this time window described in step 1, voltage and current signal is carried out Fourier decomposition, obtain the waveform collection of voltage, electric current, be the measurement window of 10 cycles due to what take in the calculation, thus can obtain harmonic wave collection N and m-Acetyl chlorophosphonazo collection N simultaneously _i, required is the harmonic wave of electric current and the harmonic wave subset of m-Acetyl chlorophosphonazo subset and voltage here;

$i_{\&perp;}=\underset{n\&Element;M}{\&Sigma;}{i}_{\&perp;n}\left(\&perp;=A,B,C\right)---\left(34\right)$

$I_{\&perp;ig.n}=\sqrt{\underset{i=2}{\overset{8}{\&Sigma;}}{I}_{\&perp;(k+i)}^2}\left(\&perp;=A,B,C\right)---\left(35\right)$

$v_{\&perp;}=\underset{n\&Element;M}{\&Sigma;}{v}_{\&perp;n}\left(\&perp;=A,B,C\right)---\left(36\right)$

Step 3: according to the voltage and current harmonic wave collection N described in step 2 and m-Acetyl chlorophosphonazo collection N _i, calculate nth harmonic and m-Acetyl chlorophosphonazo active power, n ∈ M, M are the number of times of harmonic waves all in system and m-Acetyl chlorophosphonazo subset;

$P_n=\mathrm{Re}\left\{\left(V_{An}{I}_{An}^{*}+V_{Bn}{I}_{Bn}^{*}+V_{Cn}{I}_{Cn}^{*}\right)\right\}---\left(37\right)$

Step 4: according to the nth harmonic described in step 3 and the active power direction under m-Acetyl chlorophosphonazo, harmonic wave is divided into subset N _cwith subset N _d, m-Acetyl chlorophosphonazo is divided into subset N _iCwith subset N _iD;

P _n>0, n ∈ N _cor N _iC; P _n<0, n ∈ N _dor N _iD(38)

Described subset N _c, N _iCrepresent that active power direction is harmonic wave from power supply to load and m-Acetyl chlorophosphonazo subset respectively, described subset N _d, N _iDrepresent that active power direction is harmonic wave from load to power supply and m-Acetyl chlorophosphonazo subset respectively;

Step 5: according to the subset N described in step 4 _cwith subset N _d, harmonic current subset is wherein divided into subset N _cIwith subset N _dI, according to the subset N described in step 4 _iCwith subset N _iD, m-Acetyl chlorophosphonazo electric current subset is wherein divided into forward m-Acetyl chlorophosphonazo electric current subset N _iCIwith negative sense m-Acetyl chlorophosphonazo electric current subset N _iDI;

Step 6: according to the negative sense harmonic current subset N described in step 5 _dIwith negative sense m-Acetyl chlorophosphonazo electric current subset N _iDI, for there is current i in corresponding electric current _g, and use i _gthe current harmonics cause load and m-Acetyl chlorophosphonazo are assessed;

Step 7: according to the forward harmonic current subset N described in step 5 _cIwith forward m-Acetyl chlorophosphonazo electric current subset N _iCIit is decomposed further;

Active current is

$i_a=G_{e}v=G_e{V}_0+\sqrt{2}\mathrm{Re}\underset{n\&Element;N_{CI},N_{iCI}}{\&Sigma;}{G}_e{I}^p{V}_n{e}^{{\mathrm{jn\&omega;}}_{1}t}---\left(39\right)$

Scattered current is

$i_s=(G_0-G_e)V_0+\sqrt{2}\mathrm{Re}\underset{n\&Element;N_{CI},N_{iCI}}{\&Sigma;}(G_n-G_e)I^p{V}_n{e}^{{\mathrm{jn\&omega;}}_{1}t}---\left(40\right)$

Reactive current is

$i_{rn}=\sqrt{2}\mathrm{Re}\underset{n\&Element;N_{CI},N_{iCI}}{\&Sigma;}{\mathrm{jB}}_n{1}^p{V}_n{e}^{{\mathrm{jn\&omega;}}_{1}t}---\left(41\right)$

Out-of-balance current is

$i_u^n=\sqrt{2}\mathrm{Re}\underset{n\&Element;N_{CI},N_{iCI}}{\&Sigma;}{A}_n^n{1}^n{V}_n{e}^{{\mathrm{jn\&omega;}}_{1}t}---\left(42\right)$

Zero-sequence current is

$i_u^z=\sqrt{2}\mathrm{Re}\underset{n\&Element;N_{CI},N_{iCI}}{\&Sigma;}{A}_n^z{1}^z{V}_n{e}^{{\mathrm{jn\&omega;}}_{1}t}---\left(43\right)$

Described parameter can be obtained by following formulae discovery:

Three-phase equivalent admittance is

G _e＝P/||v _n|| ²(44)

In CPC theory, be the type of attachment of star by the load equivalent of three-phase four-line system, thus its resultant admittance is Y _n=G _n+ jB _n=Y _an+ Y _bn+ Y _cn, calculate conductance and susceptance respectively:

G _n＝P _n/||v _n|| ²＝(G _An+G _Bn+G _Cn)/3,n∈N _CI,N _iCI(45)

B _n＝-Q _n/||v _n|| ²＝(B _An+B _Bn+B _Cn)/3,n∈N _CI,N _iCI(46)

Wherein, $\left|\right|v_n\left|\right|=\sqrt{{\left|\right|v_{\mathrm{An}}\left|\right|}^2+{\left|\right|v_{\mathrm{Bn}}\left|\right|}^2+{\left|\right|v_{\mathrm{Cn}}\left|\right|}^2}.$

Uneven admittance is

$A_n^n=(Y_{An}+{\mathrm{\&alpha;}}_n{Y}_{Bn}+{\mathrm{\&alpha;}}_n^{*}{Y}_{Cn})/3=A_n^n{e}^{{\mathrm{j\&psi;}}_n},n\&Element;N_{CI},N_{iCI}---\left(47\right)$

Zero sequence admittance is

$A_n^z=(Y_{An}+{\mathrm{\&alpha;}}_n^{*}{Y}_{Bn}+{\mathrm{\&alpha;}}_n{Y}_{Cn})/3=A_n^z{e}^{{\mathrm{j\&psi;}}_n},n\&Element;N_{CI},N_{iCI}---\left(48\right)$

Unit vector is

1 ^p＝[1 α ^*α] ^T，1 ⁿ＝[1 α α ^*] ^T，1 ^z＝[1 1 1] ^T。

Total voltage and electric current root-mean-square valve are

$V=\sqrt{\underset{n\&Element;M}{\&Sigma;}(V_{An}^2+V_{Bn}^2+V_{Cn}^2)}---\left(49\right)$

$I=\sqrt{\underset{n\&Element;M}{\&Sigma;}(I_{An}^2+I_{Bn}^2+I_{Cn}^2)}---\left(50\right)$

Plant factor is

${\mathrm{\&eta;}}_1=\frac{I_a}{I_N}---\left(51\right)$

Running efficiency of system is

${\mathrm{\&eta;}}_2=\frac{I_a}{I}---\left(52\right)$

Reactive current variation and frequency are

${\mathrm{\&Delta;I}}_r=\frac{dV}{Z_s}---\left(53\right)$

Step 8: the voltage and current signal gathering system PCC point place in future time window, recalculates by described step 2-7 and upgrades each current quality evaluation index;

15 values of each index obtained are combined, obtain 3s combined value by step 9: by described step 8 double counting 14 times;

Described ageing adopts the account form of root-mean-square valve.For certain current component, suppose needing to carry out in the time period of ageing, the root-mean-square valve of the n calculated 10 cycles is I _10n, then the root-mean-square valve I after ageing is

$I=\sqrt{\frac{1}{n}\underset{n}{\&Sigma;}{I}_{10n}^2}---\left(54\right)$

Step 10: repeatedly calculate by step 1-9, can obtain the 3s calculated value of each current quality evaluation index.

The current quality evaluation index system that the present invention proposes is not only applicable to monophase system, is also applicable to three-phase three-wire system and three-phase four-wire system.Its clear physical concept, clear thinking, and can be corresponding with the physical phenomenon of reality, have applied widely, highly versatile, circuit condition limits little advantage.

This embodiment is only the present invention's preferably embodiment; but protection scope of the present invention is not limited thereto; anyly be familiar with those skilled in the art in the technical scope that the present invention discloses, the change that can expect easily or replacement, all should be encompassed within protection scope of the present invention.Therefore, protection scope of the present invention should be as the criterion with the protection domain of claim.

Claims (3)

1., for a method for electric system current quality assessment, it is characterized in that, comprising:

Step 1: in each spectrum analysis time window, gathers the voltage and current signal at electric system points of common connection place;

Step 2: the voltage and current signal collected is carried out Fourier decomposition, obtains voltage and current harmonic wave collection N and m-Acetyl chlorophosphonazo collection N _i;

Step 3: according to the voltage and current harmonic wave collection N described in step 2 and m-Acetyl chlorophosphonazo collection N _i, calculate the active power of nth harmonic and m-Acetyl chlorophosphonazo, n ∈ M, M are the number of times of harmonic waves all in system and m-Acetyl chlorophosphonazo subset;

Step 4: according to the direction of the nth harmonic active power described in step 3, is divided into two subset N by harmonic wave _cwith subset N _d, m-Acetyl chlorophosphonazo is divided into two subset N _iCwith subset N _iD;

Described subset N _c, N _iCrepresent that the direction of active power is harmonic wave from power supply to load and m-Acetyl chlorophosphonazo subset respectively, described subset N _d, N _iDrepresent that the direction of active power is harmonic wave from load to power supply and m-Acetyl chlorophosphonazo subset respectively;

Step 5: according to the subset N described in step 4 _cwith subset N _d, harmonic current subset is wherein divided into forward harmonic current subset N _cIwith negative sense harmonic current subset N _dI, according to the subset N described in step 4 _iCwith subset N _iD, m-Acetyl chlorophosphonazo electric current subset is wherein divided into forward m-Acetyl chlorophosphonazo electric current subset N _iCIwith negative sense m-Acetyl chlorophosphonazo electric current subset N _iDI;

Step 6: according to the negative sense harmonic current subset N described in step 5 _dIwith negative sense m-Acetyl chlorophosphonazo electric current subset N _iDI, for there is current i in corresponding electric current _g, and use i _gthe current harmonics cause load and m-Acetyl chlorophosphonazo are assessed;

Step 7: according to the forward harmonic current subset N described in step 5 _cIwith forward m-Acetyl chlorophosphonazo electric current subset N _iCIit is decomposed further;

Situation 1, if electric system is monophase system, then decomposites active current, scattered current and reactive current; Calculate system total voltage root-mean-square valve V and electric current r.m.s. I; By active current and equipment rated current I _nradiometer calculate plant factor, calculate running efficiency of system by the radiometer of active current and electric current r.m.s. I; Variation in voltage limit value required by system, voltage root-mean-square valve V and system impedance calculate reactive current variation and frequency;

Situation 2, if electric system is three-phase three-line system, then decomposites active current, scattered current, reactive current and out-of-balance current; Calculate system total voltage root-mean-square valve V and electric current r.m.s. I; By active current and equipment rated current I _nradiometer calculate plant factor, calculate running efficiency of system by the radiometer of active current and electric current r.m.s. I; Variation in voltage limit value required by system, voltage root-mean-square valve V and system impedance calculate reactive current variation and frequency;

Situation 3, if electric system is three-phase four-wire system, then decomposites active current, scattered current, reactive current, out-of-balance current and zero-sequence current; Calculate system total voltage root-mean-square valve V and electric current r.m.s. I; By active current and equipment rated current I _nradiometer calculate plant factor, calculate running efficiency of system by the radiometer of active current and electric current r.m.s. I; Variation in voltage limit value required by system, voltage root-mean-square valve V and system impedance calculate reactive current variation and frequency;

Step 8: the voltage and current signal gathering electric system points of common connection place in future time window, recalculates by described step 2-7 and upgrades each current quality evaluation index;

Step 9: by described step 8 double counting 14 times, when equaling 200ms each computing time, carrying out seamless accumulation to 15 values of each index obtained, obtaining 3s accumulated value;

Step 10: repeatedly calculate by step 1-9 and upgrade each current quality evaluation index 3s accumulated value.

2. method according to claim 1, it is characterized in that, described each current quality evaluation index comprises economic evaluation index and restricted evaluation index; Belong to having of economic evaluation index: plant factor η ₁, running efficiency of system η ₂, reactive current i _r, zero-sequence current i _0n; Belong to having of restricted evaluation index: comprise out-of-balance current i _u, reactive current undulate quantity and frequency △ I _r, there is current i _g, scattered current i _s, m-Acetyl chlorophosphonazo electric current.

3. method according to claim 2, is characterized in that, described plant factor η ₁characterization device is utilized the ratio with transmitting active power; Described running efficiency of system η ₂characterization system is in operation the ratio of effective transmitting active power; Described reactive current i _rthe reactive power that reflected load consumes and the idle via net loss caused of transmission; Described zero-sequence current i _0nembody the unbalancedness of load and the power attenuation of the neutral line; Described out-of-balance current i _uembody the unbalancedness of load and cause the unbalancedness of voltage; Described reactive current undulate quantity and frequency △ I _rthe order of severity of reflection reactive load power variation and the fluctuation of voltage and frequency; Described generation current i _gcharacterize the current distortion that load causes; Described scattered current i _sthe current distortion that characterization system causes; Described m-Acetyl chlorophosphonazo electric current characterizes the m-Acetyl chlorophosphonazo content of system power.